I reckon there are are some very reassuring key points in your post, of which "unchanged from my previous ECG", is the most telling. Having spoken at length in the past to a heart mending chap, I remember him saying this is the most important bit of an ECG. You are built how you are built and if that doesn't change (as far as your motor is concerned) then the docs will almost certainly be happy. The machines that give an instant diagnosis work on a fairly simple standard deviation bell graph. If your heart is slightly different to Joe Average, then the machine will give its best guess at the reason and, of course, this is normally pretty well 100% accurate. However, nothing beats a properly qualified heart specialist having a gander at the squiggles and giving you the thumbs up. It's also important to remember that an ECG can only show/give an indication of what has already happened, not what might happen. This is normally the reason for a 'stress ECG', where the bods can look at your heart working under pressure and get a better idea that it is doing its job properly.
I'm not a doctor but having had many chats with a mate who is (being interested in this stuff myself) and hearing of similar stories to yours I would be willing to place a fair few liver-damaging ales on the fact that you'll be signed off as good as new.